The nematode parasite of mice, Heligmosomoides polygyrus, is able to form a chronic infection in many mouse strains. A considerable body of evidence indicates that a Th2 type of immune response can successfully terminate a primary infection, but such a response is not apparently produced by all strains of mice. The explanation for such a response dichotomy may be because specific Th2-inducing antigens are only recognized by parasite resistant strains. A candidate 16-18 kDa antigen that may induce such a response has been identified and been produced in recombinant form. It is hypothesized that this antigen can induce protective immunity in mice and these results could be extrapolated to form the basis of future vaccination studies. The aims of this proposal are to: 1. Examine the response produced by immunization of mice with the recombinant protein. 2. Vaccinate mice against the parasite using the appropriate DNA for this protein. The overall aims of this proposal are to determine whether specific antigens can induce resistance to parasitic infection and if this resistance correlates with production of a Th2 response. Furthermore, we would like to determine whether genetic immunization could induce a protective response to a specific parasitic infection. The long-term aims would be to develop a model for the protection of animals against parasitic infection, when the type of immune response required has been determined but achieving this response has proved elusive.